A typical architecture for avionic system includes several different equipment performing different functions. For example, an avionics system may:
Display flight, systems and other useful information to the crew
Record flight and system information
Include sensors that sense of the state of the aircraft (e.g.: pitch, roll, heading, altitude, airspeed, vertical speed, etc.)
Communicate with the air traffic control, other aircraft, etc.
Provide navigation functions to inform the pilot of the position of the aircraft
Other functions.
Mechanisms for routing information along different paths between avionics equipment bring benefits such as redundancy and increase in the availability of certain functions. As an example, if there are plural redundant paths, in case of failure of one path the routing system can be configured to allow the remaining path(s) to transmit information. Such configuration or reconfiguration can be either automatic (no human interaction required) or manual (e.g., using or requiring human interaction).
Ethernet-based high speed data buses have been used in avionics system. One such application is to provide data to multiple display units. In one exemplary such system for example, the Ethernet interface is cut off when one of the display units fails. In response to detection of such failure, the system may revert to using backup data communications paths. The change to backup paths may be completely automated so that no pilot action is required.
Thus, due to data bus high speed issues, data routing is commonly performed by electronic switchers or hubs. Such switchers or hubs are additional, complex electronic circuits that perform the tasks automatically. For example, ethernet switchers are very complex equipment comprising complex electronics to compute logic for routing.
It is also known to use so-called “point to point” communications between equipment. For example, it is known to use a radio port in a wireless personal communications system wherein the communication between first and second units is achieved by a digital switching device, the latter preferably a time slot interchange unit. For “point to point” connections, normal electromechanical switches can be preferred given their low cost, simplicity and high reliability. However due to switch physical characteristics, such applications in electronics equipment may be limited.
Several state-of-the-art technologies are found in the largest aircraft. However, as equipment increases in complexity, it can also have increased volume and weight. Mainly in smaller aircraft, due to weight and volume constraints, simpler solutions are generally preferred.
On the other hand, avionics high speed data buses shall comply with susceptibility to electromagnetic interference requirements. In order to reduce or isolate interference to data buses, cables with shielding and twisted wires are typically used. If a switch is installed, it can increase susceptibility to electromagnetic interference, mainly due to reduced electromagnetic shielding.
Due to potential susceptibility to electromagnetic interference of electromechanical switches and what can sometimes be rigid or at least desirable requirements for high speed data buses not to have their performance affected due to interference, the use of electromechanical switches for switching high speed avionics data buses has been avoided at least sometimes in the past.
An exemplary illustrative non-limiting implementation provides avionic systems with increased dispatch reliability wherein equipment that is part of the avionics system can be dispatched or reconfigured to be inoperative (if not required), and the information that would otherwise flow through failed or otherwise inoperative equipment can be routed to another path using at least one mechanical or electromechanical switch.
Safety can be increased since if one path (or equipment) fails or is otherwise inoperative, the switch can be changed or reconfigured (i.e., manually “switched”) in order to route information through another path(s) (e.g., to other equipment).
The exemplary illustrative non-limiting implementation relates to the use of switches for Ethernet-based aircraft data buses in avionics systems. An exemplary illustrative non-limiting solution provides manual means (through human interaction) to route the information transmitted on avionics system high speed data buses. For instance, the information path can be selected according to intentions of human beings including for example crew or maintenance people.
Considering a point-to-point data bus connection between two pieces of equipment, an exemplary illustrative non-limiting solution consists of adding an appropriate switch in the connection between those pieces of equipment. This feature can allow one or more pieces of equipment to be connected to the other terminals of the switch. Therefore, for example, depending on the switch position, it is possible to establish a connection between those two pieces of equipment, where the other pieces of equipment that are connected to open terminals of the switch remain without access to the data bus.
The use of switches for selection of avionics data bus paths provides manual selection (human interaction) of the path the information shall flow. This selection can be performed, for example, by the crew any time and/or by maintenance people on ground.
The definition of and type of switch used may depend on a selection of the most adequate or at least satisfactory switch available that can be used as part of the data bus. It is desirable to perform tests to verify the behavior of the switch and associated hardware assemblies to ensure that no interference or other problems are experienced due to use or insertion of the switch.
The number of poles of the switch may depend on the number of wires of the data bus cable. The switch can for example establish communication between equipment or access ports (for example, a panel that contains a connector for notebooks). The switch can be actuated by operation of a lever, rotary knob, push button, etc.
An exemplary illustrative non-limiting data bus may find advantageous use in aircraft wherein data buses transmit avionics information such as airspeed, altitude, position and other navigational information or another reading for maintenance or other purpose.
Example non-limiting advantages provided by use of an electromechanical switch include:
Dispatch reliability: equipment that is part of the bus can be dispatched inoperative (if not required), and the information that would flow through this failed equipment can be routed to another path using the switch.
Additional safety increase: if one path fails, the switch can be changed to route through another path(s).
Taking the example 1 of FIG. 1 (see below), in case of failure of equipment “B” but when equipment “A” continues to be healthy, “A” can continue to communicate with equipment “C”.
Increase in the availability of some functions: functions that would be lost due to a broken link can become available using another path if a switch is installed.
No additional electronic equipment and circuits are required (compare for example “hub” and “electronic switchers” of other applications).
No additional power consumption, or minimum power consumption in case of relays.
Switches have high reliability and low cost.